1. Field of the Invention
The present invention relates to a Micro Electro-Mechanical System (MEMS) switch and a method of manufacturing the same, and more particularly to an MEMS switch having a three-layer micro-structure (actuating beam) and sub-electrodes, thereby operating at low power, having high thermal stability and preventing short circuits between electrodes, and a method of manufacturing the same.
2. Description of the Related Art
In electronic systems using radio frequency bandwidth, small size, light weight and high performance products are very desirable. Thus, a very small size micro-switch realized by using new technologies has been developed widely to replace semiconductor switches such as Field Effect Transistors (FET) and PIN diodes for use in such electronic systems to control signals.
A switch is the most widely manufactured device out of the Radio Frequency (RF) devices using an MEMS technology. An RF switch is an element frequently applied to an impedance matching circuit or a signal selective transmission circuit in wireless communication terminal devices and systems using a signal in a bandwidth of microwaves or millimeter waves.
U.S. Pat. No. 6,307,169 discloses an MEMS switch which has a hinge for supporting a membrane-type electrode on a substrate. The hinge includes a control electrode coupled to the substrate by an anchor, a hinge collar and a set of hinge arms. The control electrode has a shorting bar coupled thereto and is electrically isolated from another control electrode.
Japanese Patent Laid-Open No. 2001-143595 discloses another MEMS switch which is formed on a substrate using a micro platform structure suspended on a spring suspension. The spring suspension is attached to one end of an anchor structure and extends in a substantially octagonal direction over a signal line. The micro platform has a short bar positioned facing a gap in the signal line. An electrical corset is formed over the signal line to form a capacitor structure which is electrostatically attractable toward a bottom electrode upon application of a selected voltage.
The MEMS switch described above has a drawback in that it needs a large driving voltage because it uses an electro-static force. Generally, the larger the area of an electrode, the lower the driving voltage. However, increasing the electrode area is a difficult issue because it is also desirable to have a small overall system due to the system downsizing.
Furthermore, the micro-structure, i.e. the membrane-type electrode, disclosed in U.S. Pat. No. 6,307,169 and the micro-platform-type electrode disclosed in Japanese Patent Laid-Open No. 2001-143595, need a reinforcement structure to improve thermal stability and a short circuit prevention structure to prevent a short circuit between electrodes.